Unfortunately it is pretty quick to bolt. There are supposedly slower to bolt varieties that can take a little heat, but overall I think your best bet is to sow seed every 2-3 weeks. Eventually it will become difficult to establish due to temps, but at least you always (hopefully) have some that isn't bolting for as long as you can.

I am in your zone too and see the same thing. I cut it often to prevent early bolting, when I cannot prevent it flowering anymore I let it flower and seed. Arugula will not cross with any other plant in the brassica family, it is a species of its own, so I save the seeds. I keep planting it from seed I saved. It does come true and I have not had to buy arugula seed in a long time. Keep sowing like justaguy2 said, this way you can have some new arugula coming up when some of it goes to seed. But again, it going to seed is not a bad thing necessarily, it is also really easy to harvest the seed.

You can still eat it. It's just going to be more "tart".
I go out about every other day and pluck the flowers and feed them to the neighbor's goats.
I'm having an arugula salad tonight, in fact!
Once it flowers it turns into a weed! A tasty weed. I have to pull it up from time to time so it doesn't take over the beds!

can someone tell me what the seeds look like? I have some that I deliberately let flower, now I have tall flower spikes, with very flimsy flowers...where are the seeds going to show up? How do you harvest them?

Cut the stems with the flower buds on them, and cook them like you would broccoli. They're delicious. When the stems start turning purple or the flowers open, they get very bitter.

The seed pods look like a long tiny cylinder about an inch long, and the seeds are spherical and about 1/16" in diameter.